The present invention relates to a charge sharing circuit for generating a calibration voltage. The present invention further relates to a method for generating a calibration voltage and a design structure for a charge sharing circuit.
Calibration is important for electronic circuits and in particular for mixed signal circuits.
U.S. Pat. No. 8,766,833 B1 discloses a system and method for calibrating a circuit which includes coupling a first reference voltage to a first input of the circuit and coupling a programmable reference voltage to a reference node of a digital-to-analog converter (DAC) such that the gain of the DAC is dependent on an input value at the reference node.
U.S. Pat. No. 7,609,570 B2 discloses a switched capacitor charge sharing technique for integrated circuit devices according to which a switched capacitor is used to share charge between, for example, two different signals or two different groups of signals. The size of the capacitor can be adjusted to obtain the required signal level of the various signals.
Another known way to calibrate circuits is by switching a small capacitor on a large capacitor. Such a charge sharing circuit is e.g. disclosed in U.S. Pat. No. 8,436,677 B2. More particularly, U.S. Pat. No. 8,436,677 B2 discloses a design structure for a reference voltage generator. The design structure includes a first capacitor and an analog to digital converter having its voltage reference coupled to the first capacitor. The first capacitor supplies the voltage reference to the analog to digital converter. A control loop is configured to resupply charges to the first capacitor that are lost when the first capacitor supplies the voltage reference to the analog to digital converter. The granularity of the calibration depends on the ratio of the capacitance of the capacitors that can be realized in a certain technology.
It is therefore desirable to provide improved calibration circuits and associated calibration methods.